early 15c., "act or process of becoming liquid," from French liquéfaction, from Late Latin liquefactionem (nominative liquefactio), noun of action from past participle stem of Latin liquefacere "to make liquid, melt" (see liquefy). Formerly also used in a metaphysical sense, of the melting of the soul in the ardor of devotion. Related: Liquefacient.

Whenas in silks my Julia goes,
Then, then (methinks) how sweetly flows
That liquefaction of her clothes.
[Herrick]